In some applications of the micro electro-mechanical structure, it is necessary to provide fluid in the structure, in order to utilize the characters of the fluid to provide certain functions. One example of these applications is the liquid capacitive micro inclinometer.
Taking the liquid capacitive micro inclinometer as an example, in the preparation of such a micro electro-mechanical structure, the microstructure is first formed on a substrate. The structure may further include relative circuits. Then a second substrate, preferably a glass substrate, is prepared. An enclosing space is formed on the second substrate. Fluid is then added into the enclosing space or in the microstructure. The two substrates are combined and fixed to obtain the desired inclinometer. Such process may also be used to prepare other micro electro-mechanical structures wherein fluid is used.
One example of the microstructure so prepared is described in Taiwan patent application No. 101135550, “Liquid capacitive micro inclinometer,” by the assignee of this application.
In the process described above, adhesives are used to fix the two substrates, i.e., the microstructure side substrate and the enclosing space substrate. Although there are adhesives of a variety of types usable in this process, the compatibility of the adhesive becomes one technical problem to be solved. This is because in the interface of the two substrates, materials of different physical and chemical characters are included. In addition, the photoresist materials are often used in the enclosing space side. It is difficult to select a particular adhesive that is compatible with all these materials, so to fix the two sides. In nature, micro electro-mechanical structures are structures in very tiny scale. For structures in such small scale, slight incompatibility in the interface of the two side would lead to leakage of the fluid during preparation, storage, shipment and use.
In addition, when the microstructure side substrate and the enclosing space side substrate are combined, heat and/or high pressure are used in adhering, setting and annealing. The high temperature or high pressure would gasify the fluid, leading to further leakage of the fluid, due to high gaseous pressure. The leakage does not only increase the cleaning costs but also damage the preciseness and correctness in measurement of the micro electro-mechanical components. In other words, yield rate in the preparation of the micro electro-mechanical components is damaged.
Therefore, it is necessary to provide a novel method for the preparation of micro electro-mechanical structure, without the need of adhesives in the combination of the microstructure side assembly and the enclosing space side assembly.
It is also necessary to provide a new method for the preparation of micro electro-mechanical structure that prevents leakage of fluid during the process.